In this application, it is proposed to target mutations (deletions and point mutations) into the envelope glycoprotein (env) gene of Rous sarcoma virus. Specifically, the effect of alterations in the signal sequence region and the membrane anchor/stop-translocation region of this gene will be studied. For these studies, a copy of the RSV env gene subcloned into a bacterial plasmid or the single stranded phage M13 will be used as a target for mutagenesis. Point mutations will be introduced through the use of oligonucleotide directed mutagenesis, and deletions through the use of double stranded exonuclease at suitable restriction sites. The exact location and nature of the mutations will be confirmed by DNA sequencing. The effect of mutations of the synthesis transport and function of the env gene product will be assessed in both SV40 and RSV expression vectors. These studies will provide important information on the primary amino acid sequences that are necessary for normal biosynthesis and translocation of a transmembrane protein across cellular membranes. Processes that are critical to the normal processing and secretion of a large number of cellular products. In addition, the experiments described will enhance our understanding of the synthesis of a structural protein from a group of naturally oncogenic viruses that is critical for their infectivity.